The changes of erythropoietin expression in rat brain after cerebral ischemia and reperfusion injury and its biological significance

Objectives To investigate the changes of erythropoietin(EPO)expression in rats after focal cerebral ischemia/reperfusion injury. Methods Male Sprague-Dawley rats were randomly divided into normal, sham, cerebral ischemic/reperfusion(CIR)groups.Middle cerebral artery occlusion(MACO)model was established by Longa’s method, and reperfusion was followed 2 hours after occlusion in CIR group.The rats’ brain neurological deficit scores were evaluated at 24 h, 48 h, 72 h and 96 h after reperfusion.The protein expression of EPO was determined by immunohistochemistry staining and Western blotting in each time points. Results The rats’ brain neurological deficit scores at 48 h, 72 h and 96 h were significantly increased(3.40±0.32, 3.60±0.17, 3.70±0.21, all P<0.05)compared with those at 24 h(3.00±0.22)after reperfusion in CIR group.The results of immunohistochemistry staining and Western blotting showed that the positive expression of EPO proteins in rats started at 24 h(0.36±0.05, 140.20±0.30)after cerebral ischemic/reperfusion injury, increased significantly at 48 h(1.09±0.10, 145.40±0.16), reached the peak at 72 h(1.29±0.09, 156.23±0.12), began to decline at 96 h(0.98±0.04, 141.56±0.36). Conclusions Cerebral ischemia and reperfusion injury can induce increased expression of EPO protein, which suggests that EPO may have protective effect on nerve cells under the condition of ischemia and reperfusion. Key words: Cerebral ischemia; Reperfusion injury; Cerebral ischemia; Erythropoietin